The present invention relates to an improved apparatus and method for placing a flexible tubular membrane within a body passage to shield the passage from abrasion by an instrument which is later passed through the membrane.
The invention is particularly concerned with such a membrane or sheath which may be used to accommodate the passage of instruments into delicate body passages for diagnostic or therapeutic purposes. The passages ay take the form of open body passages, such as the urethra, or normally closed body passages such as blood vessels and arteries which are entered percutaneously.
In the prior art, various techniques have been used to reduce the friction between a body passage and an instrument introduced into the passage. The most common of these use pre-dilation of the passage and/or lubrication of the instrument. Although these reduce friction between the instrument and the walls of the body passage, they do not eliminate it. Another technique is to line the body passage with a membrane or sheath which shields the passage from the instrument. With this technique, the instrument is passed through the sheath and friction between the body passage and the instrument is eliminated. U.S. Pat. No. 4,493,711 discloses a TUBULAR EXTRUSION CATHETER which provides such a membrane or sheath.